Alert archive / Mississippi / Mesoscale Discussions in 2012

Mesoscale Discussion 2010

September 30, 201211 counties in Alabama; Saint Tammany Parish, Washington Parish, Louisiana; 31 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Sep 30, 2012, 5:09 PM CDT for 11 counties in Alabama; Saint Tammany Parish, Washington Parish, Louisiana; 31 counties in Mississippi. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: Sep 30, 2012, 5:09 PM CDT (22:09 UTC)
Expired: Sep 30, 2012, 6:45 PM CDT
In force: 96 min
Issued by: the Storm Prediction Center

All 44 counties

Choctaw County, AL, Clarke County, AL, Greene County, AL, Hale County, AL, Marengo County, AL, Mobile County, AL, Monroe County, AL, Perry County, AL, Sumter County, AL, Washington County, AL, Wilcox County, AL, Saint Tammany Parish, LA, Washington Parish, LA, Clarke County, MS, Covington County, MS, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jasper County, MS, Jefferson Davis County, MS, Jones County, MS, Kemper County, MS, Lamar County, MS, Lauderdale County, MS, Lawrence County, MS, Leake County, MS, Marion County, MS, Neshoba County, MS, Newton County, MS, Noxubee County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS, Winston County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 112 km from the middle of the area, began a volume at 22:11 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 10.2 hours before the alert went out and 122 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 617 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 127 m²/s²
0-3 km storm-relative helicity: 288 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

949 
ACUS11 KWNS 302209
SWOMCD
SPC MCD 302209 
ALZ000-FLZ000-MSZ000-LAZ000-302345-

MESOSCALE DISCUSSION 2010
NWS STORM PREDICTION CENTER NORMAN OK
0509 PM CDT SUN SEP 30 2012

AREAS AFFECTED...PARTS OF SE LA...CNTRL/SRN MS AND ADJACENT W
CNTRL/SW ALABAMA

CONCERNING...TORNADO WATCH 656...

VALID 302209Z - 302345Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 656 CONTINUES.

SUMMARY...SEVERE WEATHER POTENTIAL...INCLUDING THE RISK FOR
TORNADOES...MAY INCREASE FURTHER INTO THE EVENING HOURS...INCLUDING
PORTIONS OF SOUTHWEST...PERHAPS WEST CENTRAL...ALABAMA.  WITH A
WATCH LIKELY TO BE NEEDED ACROSS AREAS EAST OF WW 656...AND SEVERE
POTENTIAL LIKELY TO CONTINUE ACROSS WW 656 BEYOND 01Z...WW  656 MAY
BE REPLACED EARLY WITH ONE NEW WATCH WITHIN THE NEXT HOUR OR SO.

DISCUSSION...WIND FIELDS...PARTICULARLY AT MID-LEVELS...ARE STILL
SOMEWHAT WEAK WITH REGARD TO SEVERE WEATHER POTENTIAL...BUT
STRENGTHENING OF SOUTHERLY 850 MB WIND FIELDS WITHIN THE WARM SECTOR
IS EXPECTED THROUGH THE 02-04Z TIME FRAME.  AS THE SUB-1000 MB
SURFACE LOW CENTER SLOWLY MIGRATES NORTHEASTWARD INTO/THROUGH
SOUTHWESTERN MISSISSIPPI DURING THE NEXT FEW HOURS...MODELS SUGGEST
THAT THE AXIS OF STRONGEST WINDS /UP TO 40+ KT/ WILL ALIGN NEAR THE
MISSISSIPPI/ALABAMA BORDER AREA.  GIVEN HIGH BOUNDARY LAYER MOISTURE
CONTENT /70F SURFACE DEW POINTS/...ENLARGING CLOCKWISE CURVED
LOW-LEVEL HODOGRAPHS MAY SUPPORT FURTHER INCREASE IN POTENTIAL FOR
TORNADOES...PARTICULARLY AS STORMS REMAIN DISCRETE IN NATURE. 
HIGHEST POTENTIAL MAY LINGER WHERE LOW-LEVEL CONVERGENCE IS ENHANCED
INLAND OF SOUTHEAST MISSISSIPPI AND SOUTHWEST ALABAMA COASTAL AREAS.

..KERR.. 09/30/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...BMX...MOB...JAN...LIX...

LAT...LON   31659042 32808986 33138905 33198834 32878722 32238716
            30918756 29948830 29988978 30289019 31049045 31659042

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 30, 5:50 PM CDT	Tornado Watch	SPC	Baldwin, Choctaw, Clarke, Conecuh, Escambia, Marengo and 5 more	8 hr
Sep 30, 10:33 AM CDT	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Lafayette and 13 more	117 min
Sep 30, 2:36 PM CDT	Tornado Watch	SPC	Ascension, East Baton Rouge, East Feliciana, Iberville, Livingston, Pointe Coupee and 6 more	3 hr

Nearby

Mesoscale Discussions in Mississippi, 2012 Mesoscale Discussions in Alabama, 2012 Mesoscale Discussions in Louisiana, 2012 Every mesoscale discussion in 2012

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.